Mitigating routing misbehavior in mobile ad hoc networks

Editor's Notes

• #11: Figure 1 illustrates route discovery. Node S (the source) wishes to communicate with node D (the destination) but does not know any paths to D. S initiates a route discovery by broadcasting a route request packet to its neighbors that contains the destination address D. The neighbors in turn append their own addresses to the route request packet and rebroadcast it. This process continues until a route request packet reaches D. D must now send back a route reply packet to inform S of the discovered route. Since the route request packet that reaches D contains a path from S to D, D may choose to use the reverse path to send back the reply (bidirectional links are required here) or to initiate a new route discovery back to S. Since there can be many routes from a source to a destination, a source may receive multiple route replies from a destination. DSR caches these routes in a route cache for future use.
• #12: *Source Route **Route Cache ***Route Discovery ****Target and Initiator *****Route Reply ******( Initiator Address and Request ID ) Source wanna send packet to Destination a.
• #15: Figure 2 illustrates how the watchdog works. Suppose there exists a path from node S to D through intermediate nodes A, B, and C. Node A cannot transmit all the way to node C, but it can listen in on node B's traffic. Thus, when A transmits a packet for B to forward to C, A can often tell if B transmits the packet. If encryption is not performed separately for each link, which can be expensive, then A can also tell (know) if B has tampered with the payload or the header. many wireless networks utilize a hop-by-hop acknowledgement at the data link level in order to provide early detection and retransmission of lost or corrupted packets For example, in Figure 1, host A may be able to hear B’s transmission of the packet on to C. This type of acknowledgement is known as a passive acknowledgement [11].
• #16: many wireless networks utilize a hop-by-hop acknowledgement at the data link level in order to provide early detection and retransmission of lost or corrupted packets For example, in Figure 1, host A may be able to hear B’s transmission of the packet on to C. This type of acknowledgement is known as a passive acknowledgement [11]. Half duplex operation: transmit packet, go into receive mode, receive ack, receive next packet, go into transmit mode, repeat Original sender hears forwarding transmission from next hop node in the route:Power control: transmit with enough power to be heard at D as well as F In addition, existing transport or application level replies or acknowledgements from the original destination could also be used as an acknowledgement that the route (or that hop of the route) is still working. As a last resort, a bit in the packet header could be included to allow a host transmitting a packet to request an explicit acknowledgement from the next-hop receiver. If no other acknowledgement signal has been received in some time from the next hop on some route, the host could use this bit to inexpensively probe the status of this hop on the route.
• #17: many wireless networks utilize a hop-by-hop acknowledgement at the data link level in order to provide early detection and retransmission of lost or corrupted packets For example, in Figure 1, host A may be able to hear B’s transmission of the packet on to C. This type of acknowledgement is known as a passive acknowledgement [11]. Half duplex operation: transmit packet, go into receive mode, receive ack, receive next packet, go into transmit mode, repeat Original sender hears forwarding transmission from next hop node in the route:Power control: transmit with enough power to be heard at D as well as F In addition, existing transport or application level replies or acknowledgements from the original destination could also be used as an acknowledgement that the route (or that hop of the route) is still working. As a last resort, a bit in the packet header could be included to allow a host transmitting a packet to request an explicit acknowledgement from the next-hop receiver. If no other acknowledgement signal has been received in some time from the next hop on some route, the host could use this bit to inexpensively probe the status of this hop on the route.
• #19: The ambiguous collision problem prevents A from overhearing transmissions from B. As Figure 3 illustrates, a packet collision can occur at A while it is listening for B to forward on a packet. A does not know if the collision was caused by B forwarding on a packet as it should or if B never forwarded the packet and the collision was caused by other nodes in A's neighborhood. Because of this uncertainty, A should not immediately accuse B of misbehaving, but should instead continue to watch B over a period of time. If A repeatedly fails to detect B forwarding on packets, then A can assume that B is misbehaving.
• #20: Another problem can occur when nodes falsely report other nodes as misbehaving. A malicious node could attempt to partition the network by claiming that some nodes following it in the path are misbehaving. For instance, node A could report that node B is not forwarding packets when in fact it is. This will cause S to mark B as misbehaving when A is the culprit. This behavior, however, will be detected. Since A is passing messages on to B (as verified by S), then any acknowledgements from D to S will go through A to S, and S will wonder why it receives replies from D when supposedly B dropped packets in the forward direction. In addition, if A drops acknowledgements to hide them from S, then node B will detect this misbehavior and will report it to D Another problem is that a misbehaving node that can control its transmission power can circumvent the watchdog. A node could limit its transmission power such that the signal is strong enough to be overheard by the previous node but too weak to be received by the true recipient. This would require that the misbehaving node know the transmission power required to reach each of its neighboring nodes. Only a node with malicious intent would behave in this manner selfish nodes have nothing to gain since battery power is wasted and overloaded nodes would not relieve any congestion by doing this.
• #22: The pathrater, run by each node in the network, combines knowledge of misbehaving nodes with link reliability data to pick the route most likely to be reliable. Each node maintains a rating for every other node which knows about in the network. It calculates a path metric by averaging the node ratings in the path. We choose this metric because it gives a comparison of the overall reliability of different paths and allows pathrater to emulate the shortest length path algorithm when no reliability information has been collected, as explained below. If there are multiple paths to the same destination, we choose the path with the highest metric. Note that this differs from standard DSR, which chooses the shortest path in the route cache. Further note that since the pathrater depends on knowing the exact path that a packet has traversed, it must be implemented on top of a source routing protocol.The pathrater assigns ratings to nodes according to the following algorithm. Pathrather know status of every node through route discovery 2. The Pathrather assigns it a neutral rating of 0.5 3. A node always rates itself with a 1.0 4. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. 5. When a node in the network becomes known to the pathrater (through route discovery), the pathrater assigns it a neutral rating of 0.5. A node always rates itself with a 1.0. This ensures that when calculating path rates, if all other nodes are neutral nodes (rather than suspected misbehaving nodes), the pathrater picks the shortest length path. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. An actively used path is one on which the node has sent a packet within the previous rate increment interval. The maximum value a neutral node can attain is 0.8. We decrement a node's rating by 0.05 when we detect a link break during packet forwarding and the node becomes unreachable. The lower bound rating of a neutral node is 0.0. The pathrater does not modify the ratings of nodes that are not currently in active use. We assign a special highly negative value,
• #23: The pathrater, run by each node in the network, combines knowledge of misbehaving nodes with link reliability data to pick the route most likely to be reliable. Each node maintains a rating for every other node which knows about in the network. It calculates a path metric by averaging the node ratings in the path. We choose this metric because it gives a comparison of the overall reliability of different paths and allows pathrater to emulate the shortest length path algorithm when no reliability information has been collected, as explained below. If there are multiple paths to the same destination, we choose the path with the highest metric. Note that this differs from standard DSR, which chooses the shortest path in the route cache. Further note that since the pathrater depends on knowing the exact path that a packet has traversed, it must be implemented on top of a source routing protocol.The pathrater assigns ratings to nodes according to the following algorithm. Pathrather know status of every node through route discovery 2. The Pathrather assigns it a neutral rating of 0.5 3. A node always rates itself with a 1.0 4. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. 5. When a node in the network becomes known to the pathrater (through route discovery), the pathrater assigns it a neutral rating of 0.5. A node always rates itself with a 1.0. This ensures that when calculating path rates, if all other nodes are neutral nodes (rather than suspected misbehaving nodes), the pathrater picks the shortest length path. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. An actively used path is one on which the node has sent a packet within the previous rate increment interval. The maximum value a neutral node can attain is 0.8. We decrement a node's rating by 0.05 when we detect a link break during packet forwarding and the node becomes unreachable. The lower bound rating of a neutral node is 0.0. The pathrater does not modify the ratings of nodes that are not currently in active use. We assign a special highly negative value,
• #24: The pathrater, run by each node in the network, combines knowledge of misbehaving nodes with link reliability data to pick the route most likely to be reliable. Each node maintains a rating for every other node which knows about in the network. It calculates a path metric by averaging the node ratings in the path. We choose this metric because it gives a comparison of the overall reliability of different paths and allows pathrater to emulate the shortest length path algorithm when no reliability information has been collected, as explained below. If there are multiple paths to the same destination, we choose the path with the highest metric. Note that this differs from standard DSR, which chooses the shortest path in the route cache. Further note that since the pathrater depends on knowing the exact path that a packet has traversed, it must be implemented on top of a source routing protocol.The pathrater assigns ratings to nodes according to the following algorithm. Pathrather know status of every node through route discovery 2. The Pathrather assigns it a neutral rating of 0.5 3. A node always rates itself with a 1.0 4. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. 5. When a node in the network becomes known to the pathrater (through route discovery), the pathrater assigns it a neutral rating of 0.5. A node always rates itself with a 1.0. This ensures that when calculating path rates, if all other nodes are neutral nodes (rather than suspected misbehaving nodes), the pathrater picks the shortest length path. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. An actively used path is one on which the node has sent a packet within the previous rate increment interval. The maximum value a neutral node can attain is 0.8. We decrement a node's rating by 0.05 when we detect a link break during packet forwarding and the node becomes unreachable. The lower bound rating of a neutral node is 0.0. The pathrater does not modify the ratings of nodes that are not currently in active use. We assign a special highly negative value,
• #25: The pathrater, run by each node in the network, combines knowledge of misbehaving nodes with link reliability data to pick the route most likely to be reliable. Each node maintains a rating for every other node which knows about in the network. It calculates a path metric by averaging the node ratings in the path. We choose this metric because it gives a comparison of the overall reliability of different paths and allows pathrater to emulate the shortest length path algorithm when no reliability information has been collected, as explained below. If there are multiple paths to the same destination, we choose the path with the highest metric. Note that this differs from standard DSR, which chooses the shortest path in the route cache. Further note that since the pathrater depends on knowing the exact path that a packet has traversed, it must be implemented on top of a source routing protocol.The pathrater assigns ratings to nodes according to the following algorithm. Pathrather know status of every node through route discovery 2. The Pathrather assigns it a neutral rating of 0.5 3. A node always rates itself with a 1.0 4. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. 5. When a node in the network becomes known to the pathrater (through route discovery), the pathrater assigns it a neutral rating of 0.5. A node always rates itself with a 1.0. This ensures that when calculating path rates, if all other nodes are neutral nodes (rather than suspected misbehaving nodes), the pathrater picks the shortest length path. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. An actively used path is one on which the node has sent a packet within the previous rate increment interval. The maximum value a neutral node can attain is 0.8. We decrement a node's rating by 0.05 when we detect a link break during packet forwarding and the node becomes unreachable. The lower bound rating of a neutral node is 0.0. The pathrater does not modify the ratings of nodes that are not currently in active use. We assign a special highly negative value,
• #26: The pathrater, run by each node in the network, combines knowledge of misbehaving nodes with link reliability data to pick the route most likely to be reliable. Each node maintains a rating for every other node which knows about in the network. It calculates a path metric by averaging the node ratings in the path. We choose this metric because it gives a comparison of the overall reliability of different paths and allows pathrater to emulate the shortest length path algorithm when no reliability information has been collected, as explained below. If there are multiple paths to the same destination, we choose the path with the highest metric. Note that this differs from standard DSR, which chooses the shortest path in the route cache. Further note that since the pathrater depends on knowing the exact path that a packet has traversed, it must be implemented on top of a source routing protocol.The pathrater assigns ratings to nodes according to the following algorithm. Pathrather know status of every node through route discovery 2. The Pathrather assigns it a neutral rating of 0.5 3. A node always rates itself with a 1.0 4. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. 5. When a node in the network becomes known to the pathrater (through route discovery), the pathrater assigns it a neutral rating of 0.5. A node always rates itself with a 1.0. This ensures that when calculating path rates, if all other nodes are neutral nodes (rather than suspected misbehaving nodes), the pathrater picks the shortest length path. The pathrater increments the ratings of nodes on all actively used paths by 0.01 at periodic intervals of 200 ms. An actively used path is one on which the node has sent a packet within the previous rate increment interval. The maximum value a neutral node can attain is 0.8. We decrement a node's rating by 0.05 when we detect a link break during packet forwarding and the node becomes unreachable. The lower bound rating of a neutral node is 0.0. The pathrater does not modify the ratings of nodes that are not currently in active use. We assign a special highly negative value,
• #27: • Assumptions – Bidirectional communication – Wireless interfaces that support promiscuous mode operation • Setup – 50 nodes in various states of mobility – Created 4 different extension scenarios (WD, PR, SRR) – Varied misbehaving nodes 0% to 40%
• #28: • Assumptions – Bidirectional communication – Wireless interfaces that support promiscuous mode operation • Setup – 50 nodes in various states of mobility – Created 4 different extension scenarios (WD, PR, SRR) – Varied misbehaving nodes 0% to 40%
• #29: While a network with 40% misbehaving nodes may seem unrealistic, it is interesting to study the behavior of the algorithms in a more hostile environment than we hope to encounter in a real life.
• #30: • Evaluation done on three metrics: – Throughput: % of sent data actually received by the intended destinations – Overhead: Ratio of routing-related transmission to data transmissions – Watchdog False Positives: The impact when watchdog mistakes a node as misbehaving
• #32: • Best performance when all three extensions were active • Pathrater isolated in one test • Pathrater alone does not affect performance
• #33: • Best performance when all three extensions were active • Pathrater isolated in one test • Pathrater alone does not affect performance
• #36: • Increased overhead • Watchdog isolated in one simulation • Watchdog alone adds a little overhead
• #37: c
• #40: • Demonstrated how throughput is effected with the reporting of False Positives • Throughput does decrease but could result in beneficial side effects: – Helps determine unreliable nodes – Ambiguous collisions may help increase throughput – Nodes maintain a fresher route cache
• #41: c
• #42: c
• #43: c
• #45: Note that the simulations in this paper uses CBR data sources with no reliability requirements.